Profits Are Soaring. The Stock Market Has Barely Noticed.

Earnings season is underway on Wall Street and, thanks to a heady combination of core business strength and tax windfalls, the results have been exceptional.

In fact, based on the numbers so far, profits among the biggest American corporations are growing so fast that you may expect the stock market to be soaring like a rocket.

That’s not the direction the market has been heading, of course. Since February, most stocks have been sluggish — or downright negative — and the spectacular earnings reports have received less fanfare than they probably deserve.

There are valid reasons for the market’s lack of response, the main one being that by February the market had gotten way ahead of itself, reaching valuations that few people could justify. Stocks rose so rapidly in 2017 and early 2018 — on top of their increases since 2009 — that prices had begun to seem impossibly high.

Add the negative impact of rising interest rates and heightened expectations for inflation — both of which tend to hurt share prices — and it’s easy to see why the stock market weakened as much as it did.

Yet the reality is that earnings growth has been extraordinary so far this year. That superlative performance won’t continue forever — that’s no more possible than eternal youth. Next year, in fact, the tax effect is expected to subtract from earnings growth when this year’s windfalls are baked into financial statements.

But it’s still worth noting how good this season has been and what it may portend for the next year or two. For people who have been concerned that stock valuations had gotten out of whack and that the threat of a trade war imperils the economy — and I’d place myself in that camp — the earnings surge provides some comfort.

Tax windfalls are certainly inflating the numbers, but the core earnings of American corporations look solid, nonetheless.

Consider the picture for the first three months of 2018, the period for current earnings reports. By one measure, the quarter is actually turning out to have been the best for corporate America in decades. The tax cuts that went into effect this year have transformed excellent earnings into exceptional ones.

David Aurelio, a senior research analyst for Thomson Reuters, says nearly 80 percent of the companies in the Standard & Poor’s 500-stock index that have reported so far have outstripped the expectations of Wall Street — 16 percentage points higher than the average number of companies that beat expectations. “That performance is the best since our records started in 1994,” he said.

Earnings per share have grown 26 percent since the same quarter a year earlier, according to Thomson Reuters I/B/E/S data. Net operating income — essentially, profit after taxes — has risen nearly 25 percent in the same period. Almost half of that gain, 11.6 percentage points, comes from the big cut in corporate taxes that took effect this year.

The tax windfall alone accounts for a larger earnings increase than the stock market typically receives from conventional sources, the data shows. Expectations of a tax cut may help explain the run-up in stocks in 2017 and earlier this year.

But writing off the current earnings surge entirely as a pure artifact of tax cuts would be a mistake. Before taxes, earnings grew 13.2 percent for the quarter. That is a breathtaking figure.

“Whenever you get double-digit earnings growth coming from core earnings, it is really healthy,” Mr. Aurelio said. “What I find surprising is that, aside from the tax cuts, fundamentals are really looking strong,” he added.

Take Apple, the world’s most valuable publicly traded company. When it reported its most recent quarterly earnings on May 1, the results were remarkable: a 25.3 percent increase in net income over the same quarter a year earlier.

More than half of that improvement came from tax windfalls. In its financial statement, the company reduced its expected tax liability for the period — technically, its provision for taxes — by more than 35 percent. And in a conference call, Apple executives said that thanks to the new law, the company’s effective tax rate has dropped to 14.5 percent. It was 25.5 percent in the same period last year, they said.

The tax changes mean that Apple suddenly has “increased financial and operational flexibility from the access to our global cash,” which had been stranded abroad, said Luca Maestri, Apple’s chief financial officer. So Apple announced a $100 billion increase in what had been a $300 billion share buyback program, as well as a 16 percent dividend increase.

All of that is a boon to shareholders. But what is probably more important is that the iPhone and other core businesses continue to churn out staggering profits even after stripping away the effects of taxes.

Apple’s operating income rose more than 10 percent in the quarter, an impressive figure in its own right, and the end of the Apple profit machine is nowhere in sight.

Apple isn’t the only company to have churned out outstanding earnings. Profits have been rising for most big American companies, and Wall Street expects that to continue for at least the next year or two.

Edward Yardeni, an independent market strategist, points out that double-digit earnings growth isn’t likely to be sustained by corporate America. Profit growth is likely to decline to the roughly 7 percent annual rate that has been the historic norm, he says. And the norm is that stock market will rise at about that rate over the long run. He expects that to continue.

While the market has barely noticed the current avalanche of profits, the combination of stagnant prices and rising earnings means that market valuations have already improved rapidly. If that trend continues, many stocks will again begin to look like bargains.